Plastic containers such as bottles of water are manufactured and filled according to different methods including blow molding or stretch-blow molding.
According to one of these known methods a plastic preform is first manufactured through a molding process and then heated before being positioned inside a mold.
The preform usually takes the form of a cylindrical tube closed at its bottom end and open at its opposite end.
Once the preform has been positioned within the mold only the open end of the preform is visible from above the mold.
This method makes use of a stretch rod which is downwardly engaged into the open end of the preform so as to abut against the closed bottom end thereof. The stretch rod is further actuated to be urged against the closed end, thereby resulting in stretching the preform.
After the stretching phase has been initiated a liquid is also injected into the preform through its open end. This liquid injection causes expansion of the preform until coming into contact with the inner walls of the mold, thereby achieving the final shape of the bottle.
When the liquid injected into the perform contains dissolved gas, such as sparkling water or any other carbonated beverage, venting of the opening of the bottle to atmospheric pressure has to be performed before closing the opening with a cap.
Today, venting to atmospheric pressure is currently being performed by opening a communication channel between the opening of the bottle and the ambient atmospheric pressure. In the field of bottle blowing this process is referred to as a degasification process.
However, there exists a need for an improved method enabling degasification or venting to atmospheric pressure of a container filled with a carbonated beverage.